Dilatation balloon catheters are well known and used regularly for coronary angioplasty procedures and other similar procedures. Atheromatous plaque adhering to a blood vessel wall and restricting blood flow therethrough is compressed against the vessel wall by a balloon that is positioned in the vessel at the plaque location. This dilates the vessel lumen to permit increased blood flow.
A typical balloon catheter includes two lengthwise lumens or channels, one for inflation of an inflatable balloon sealed to the distal catheter end and the other for insertion of a guidewire extending through the catheter to aid in positioning the catheter during use.
Many catheters have been designed for particular uses, having a variety of configurations, methods of construction and methods of use. Most have a generally tubular balloon that, when inflated, temporarily cuts off blood flow through the vessel. Serious consequences can occur when blood flow is stopped for an extended period. Therefore, inflation duration is generally relatively short, typically no more than 150-180 seconds. Longer inflation periods would be very desirable, since better plaque compression could be accomplished. Also, some patients cannot tolerate even short time blood occlusion in some vessels.
Attempts have been made to develop balloon configurations that will permit at least some continued blood flow during plaque compression. For example, catheters having an additional lumen have been used, with openings between the catheter exterior and the added lumen at both ends of the balloon, so that limited blood flow can bypass the balloon occlusion. However, this arrangement has had limited success, since only a very limited amount of blood can flow though the lumen and adding the lumen increases the diameter of the catheter, which itself will tend to retard blood flow. Thus, at most this arrangement will allow a very slightly longer balloon inflation period.
Blackshear et al. in U.S. Pat. No. 5,308,356 and others have disclosed catheter balloons with a spiral or corkscrew-like configuration when expanded. Such perfusion balloon catheters are intended to allow blood to flow in a spiral channel path past the balloon during balloon inflation. However, in practice, little if any blood flow is found to occur with these spiral balloons, apparently due to blockage of the balloon channels by the arterial intima or lining. Other spiral balloons have been used for other purposes, such as the Fogarty et al. arrangement described in U.S. Pat. No. 4,762,130 for embolectomy.
In attempting to overcome these channel blockage problems, generally tubular sheaths have been provided over the spiral balloon, as disclosed by Gurbel et al. in U.S. Pat. No. 5,295,959 and by Cordis in U.S. Pat. No. 5,484,411. These sheaths cover the outer portions of the balloon spiral lobe and resist entry of arterial intima into the spiral channels when the balloon is inflated. While often effective in increasing blood flow past the balloon, these sheaths are typically unbonded or only bonded by heat or adhesive to narrow lines along the balloon spiral and may come loose in use in a blood vessel, to the serious detriment of the patient. Further, "tenting" also occurs in the middle channels of a spiral balloon, with the sheath tending to fold into the channel, where the sheath is not bonded to the spiral under tension.
Such sheaths are also difficult to manufacture in a manner that will resist tearing of sheath end edges when in use and when being moved along a vessel to the desired location. Ends of the sheath that are located at narrower balloon end regions may result in the sheath ends folding or "tenting" into the spiral channels, decreasing blood flow. Any tears at the sheath ends will aggravate this channel blocking tendency.
A spiral wire may be contained within a spiral channel along the surface of a balloon to prevent the channel from stretching sufficiently to significantly decrease the channel cross section and severely reduce perfusion. While the spiral wire is generally effective in preventing channel expansion, the wire occupies space best used for perfusion. Also, the wire makes the balloon stiffer, interfering with tracking and making reaching a lesion more difficult. The balloon profile will be larger and rewrap will be more difficult.
Therefore, there is a continuing need for improvements in perfusion dilatation catheters manufacturing apparatus and methods of improved manufacturing efficiency and simplicity that provide improved balloon geometry, catheters that permit increased blood flow past the inflated balloon while maintaining the desired dilatation effect with respect to plaque or the like, that form perfusion channels having improved resistance to channel blockage, that allow improved tracking during insertion, and provide a smaller profile and improved rewrap.